On Sun, Apr 08, 2018 at 09:25:33PM +1000, Nick Coghlan wrote:
I was writing a new stdlib test case today, and thinking about how I might structure it differently in a PEP 572 world, and realised that a situation the next version of the PEP should discuss is this one:
# Dict display data = { key_a: 1, key_b: 2, key_c: 3, }
# Set display with local name bindings data = { local_a := 1, local_b := 2, local_c := 3, }
I don't understand the point of these examples. Sure, I guess they would be legal, but unless you're actually going to use the name bindings, what's the point in defining them? data = { 1, (spam := complex_expression), spam+1, spam*2, } which I think is cleaner than the existing alternative of defining spam outside of the set. And for dicts: d = { 'key': 'value', (spam := calculated_key): (eggs := calculated_value), spam.lower(): eggs.upper(), }
I don't think this is bad (although the interaction with dicts is a bit odd), and I don't think it counts as a rationale either, but I do think the fact that it becomes possible should be noted as an outcome arising from the "No sublocal scoping" semantics.
If we really wanted to keep the sublocal scoping, we could make list/set/dict displays their own scope too. Personally, that's the only argument for sublocal scoping that I like yet: what happens inside a display should remain inside the display, and not leak out into the function. So that has taken me from -1 on sublocal scoping to -0.5 if it applies to displays. -- Steve